Step-up voltage transformer having high tension lead



Aug. 24, 1965 R. PENN 3,202,950

STEP-UP VOLTAGE TRANSFORMER HAVING HIGH TENSION LEAD Filed Dec. 28, 1959lA/VENTOR R EGINALD PENN VWZ ATTOR/V Y 3,202,950 STEP-UP VOLTAGETRANSFORMER HAVING HlGH TENSION LEAD Reginald Penn, Bletchley, England,assignor to Wipac Development Limited, London, England, a Britishcompany I Filed Dec. 28, 1959, Ser. No. 862,380 Claims priority,application Great Britain, May 22, 1959, 17,607/ 59 2 Claims. (Cl.336-192) The present invention relates to transformers suitable for useas voltage step-up transformers in ignition systems of the typecomprising a capacitor connected to be charged from a source ofelectrical energy, and the primary wind ing of a voltage step-uptransformer connected in a discharge circuit of the capacitor throughmake-and-break contacts, the voltage appearing across the secondarywinding of the transformer being suitable for application to a sparkingplug of an internal combustion engine to effect ignition.

According to the present invention, a transformer suitable for use as avoltage step-up transformer in an ignition system of the type specified,comprises a low-loss ferromagnetic core mounted in a former ofelectrically-insulating material, the former being longer than the coreand being arranged with its ends projecting beyond the ends of the core,a multi-layer secondary winding being wound on the former, and over thesecondary winding a single-layer primary winding connected end-to-endwith the secondary winding at the outermost layer of the latter, theaxial lengths of the primary and secondary windings being substantiallyequal to one another and equal to or less than the length of the coreand the windings being disposed With the centre of the windings and thecentre of the core substantially coincident whereby the ends of theformer project beyond the endsof the windings, and a high-tensionconnection to the secondary winding passing between the core and theformer and through an aperture in the central region of the former tothe innermost layer of the secondary winding. A low-loss, ferro-magneticcore is, for the purpose of this specification, a core of ferritematerial, particles of ferro-magnetic material in a binder, or the like.

The invention will now be described, by way of example, with referenceto the accompanying drawing which is a schematic, longitudinalcross-section of a transformer.

The transformer shown comprises a cylindrical ferrite core 10, 0.5625inch long and 0.124 inch diameter. This is inside a cylindrical tube orformer 11 of insulating material 0.75 inch long, 0.13 inch internaldiameter and 0.15 inch external diameter, the ends of the core beingequidistant from the corresponding ends of the tube 11. Wound over thetube 11 there is a multi-layer secondary winding 12 and a single-layerprimary winding 13 lying over the secondary winding 12.

The secondary winding is provided with a lead-out wire 14 which passesthrough a central aperture 15 in a discshaped, insulating end-plate 16.The connecting wire 14 passes between the core and the tube 11 for abouthalf the length of the tube 11 and then through an aperture 17 in thecenter of the tube 11 to the secondary winding 12.

The secondary winding 12 is of 47 S.W.G. enameled copper wire andapartfrom the first layer directly on the tube 11 has layers as showneach layer containing 193 turns. The first layer 18 has only a fewturns, say three,

United States Patent 0 ice which are widely spaced. The primary windingand each layer of the secondary winding are shown to be of the sameaxial length as the core 10 but could be somewhat shorter than the core.

Over each layer of the secondary winding there is provided a layer ofinsulating paper and these layers extend to the end of the tube 11 asshown at 19.

The outermost end 20 of the secondary winding is connected to one end ofthe primary winding which has 33 turns of 36 S.W.G. enameled copperwire.

A lead-in wire 21 is provided to the junction of the two windings and afurther lead-in wire 22 is provided to the other end of the primarywinding.

The transformer described although of simple and cheap construction hasproved, when impregnated with solvent less varnish, to give reliable andeffective service in an ignition system of the type hereinbeforespecified. Many forms of such an ignition system have been proposed butnone have proved to be a commercial success. One of the factors in theirlack of success has been the provision of a reliable transformer ofsimple and cheap construction. The present invention has been found tomeet this need.

I claim:

1. A transformer suitable for use as a voltage step-up transformer in anignition system of the type specified, comprising a low-loss,ferro-magnetic core mounted in a former of electrically-insulatingmaterial, the former being longer than the core and being arranged withits ends projecting beyond the ends of the core, a multi-layer secondarywinding being wound on the former, and over the secondary winding asingle-layer primary winding having one end connected with the end ofthe secondary winding at the outermost layer of the latter, the axiallengths of the primary and secondary windings being substantially equalto one another and at most equal to the length of the core and thewindings being disposed with the centres of the windings and the centresof the core substantially coincident whereby the ends of the formerproject beyond the ends of the windings, and a high-tension connectionto the secondary winding passing between the core and the former andthrough an aperture in the former substantially equidistant from theends of the former to the innermost layer of the secondary winding.

2. A transformer suitable for use as a voltage step-up transformer in anignition system of the type specified, comprising a low-loss,term-magnetic core mounted in a former of electrically-insulatingmaterial, the former being longer than the core and being arranged withits ends projecting beyond the ends of the core, a multi-layer secondarywinding being wound on the former, an insulating layer axiallycoextensive with said former over each layer of said secondary windingand over the secondary winding a single-layer primary winding having oneend connected with the end of the secondary winding at the outermostlayer of the latter, the axial lengths of the primary and secondarywindings being substantially equal to one another and at most equal tothe length of the core and the windings being disposed with the centresof the windings and the centre of the core substantially coincidentwhereby the ends of the former project beyond the ends of the windings,and a high-tension connection to the secondary winding passing adjacentto the core within the former and through an aperture in the former tothe innermost layer of the secondary winding and a disc-shapedinsulating end plate overlying the ends of said former and ReferencesCited by the Examiner UNITED STATES PATENTS 5/00 Varley 336-208 6/18Jacobson 336-198 Cavanagh 317-15762 Cragg 317-1576 Carbenay 336-198Crowley 336-233 DARRELL L. CLAY, Primary Examiner.

MILTON O.'HIRSHFIELD, ORRIN L. RADER, E.

JAMES SAX, JOHN F. BURNS, Examiners.

1. A TRANSFORMER SUITABLE FOR USE AS A VOLTAGE STEP-UP TRANSFORMER IN ANIGNITION SYSTEM OF THE TYPE SPECIFIED, COMPRISING A LOW-LOSS,FERRO-MAGNETIC CORE MOUNTED IN A FORMER OF ELECTRICALLY-INSULATINGMATERIAL, THE FORMER BEING LONGER THEN THE CORE AND BEING ARRANGED WITHITS ENDS PROJECTING BEYOND THE ENDS OF THE CORE, A MULTI-LAYER SECONDARYWINDING BEING WOUND ON THE FORMER, AND OVER THE SECONDARY WINDING ASINGLE-LAYER PRIMARY WINDING HAVING ONE END CONNECTED WITH THE END OFTHE SECONDARY WINDING AT THE OUTERMOST LAYER OF THE LATTER, THE AXIALLENGTHS OF THE PRIMARY AND SECONDARY WINDINGS BEING SUBSTANTIALLY EQUALTO ONE ANOTHER AND AT MOST EUAL TO THE LENGTH OF THE CORE AND THEWINDINGS BEING DISPOSED WITH THE CENTRES OF THE WINDINGS AND THE CENTRESOF THE CORE SUBSTANTIALLY COINCIDENT WHEREBY THE ENDS OF THE FORMERPROJECT BEYOND THE ENDS OF THE WINDINGS, AND A HIGH-TENSION CONNECTIONTO THE SECONDARY WINDINGS PASSING BETWEEN THE CORE AND THE FORMER ANDTHROUGH AN APERTURE IN THE FORMER SUBSTANTIALLY EQUIDISTANT FROM THEENDS OF THE FORMER TO THE INNERMOST LAYER OF THE SECONDARY WINDINGS.